You're nearly there, actually. In the remittance layout, go to tools, options and then choose the email setup tab. Under Default Provider, pull down the list and choose MAPI if it's available. On the lower section 'Available Providers' click MAPI then 'Configure' and check the box for 'Use Default Profile'. If you have a regular MS Exchange email system, this should work.
When you run your remittances to email now, they will go into your Inbox in Outlook as drafts, ready for your to open each one and hit 'send'. It doesn't send them automatically, and this is a quirk of Outlook, rather than Sage (as far as I know).
Hope this helps.